WHO’S YOUR PADRE? Mets pitcher Matt Harvey, who starts tonight at Citi Field against the Padres, gave up five runs in five innings in his only start vs. San Diego last year. Photo: Getty Images

Matt Harvey aced his freshman finals, but now has to avoid succumbing to the sophomore slide.

The Mets figure the prized right-hander has an excellent chance of succeeding, after he spent the offseason and spring training perfecting a new changeup to complement his raw heat.

When the first pitch is thrown tonight at Citi Field, the Padres will be seeing a more complete pitcher than the one they hammered last August at Petco Park, in Harvey’s third major league start.

Overall, Harvey finished his rookie season 3-5 with a 2.73 ERA in 10 starts for the Mets, with 70 strikeouts, 26 walks and 42 hits allowed in 59 1/3 innings. Those numbers excited the Mets, but they were not complacent in the offseason with the stud fireballer.

“Matt Harvey, when the season was over, was told, ‘Your changeup is another pitch you need to use,’ ” manager Terry Collins said. “And all he did was come to spring training, worked hard and used it and became a very effective pitcher, so he has made adjustments himself, already.”

Though Jon Niese carries the ceremonial title of “ace” with Johan Santana no longer in the picture, the battle for the top spot figures to heat up this summer, between the 24-year-old Harvey and top pitching prospect Zack Wheeler, who is starting the season at Triple-A Las Vegas.

Niese set the tone in Monday’s opener by holding the Padres to two runs over 6 2/3 innings in the Mets’ 11-2 victory.

“All five of us are in a row, so we’re all pushing each other,” Harvey said. “We’re all, not necessarily trying to one up each other, but it’s a competitive group and we all want to do well, and obviously Niese’s strong performance [Monday] pushes all five of us to go out and pitch [well].”

Harvey doesn’t want to hear anything about the chilly forecast for Citi Field tonight.

“I’m from Connecticut, so I’ve pitched in cold,” the Groton, Conn., native said. “You’ve got to block it out just as you do anything else. It’s going to be cold, but you can’t make any excuses — you’ve got to go out there and perform and do your job.”

Harvey bombed against the Padres last Aug. 5, allowing five runs on eight hits and two homers over five innings. It was the only start last season in which Harvey allowed more than three runs. But still missing from his resume is a victory at Citi Field, where the Mets scored four total runs in his four starts last season.

Harvey wants to work deeper into games, putting himself in position for more victories. Last year he completed seven innings just twice in his 10 starts.

“The way he pitched in spring training, pounded the strike zone and made people swing the bats, he’s going to get easier outs,” Collins said. “I see him getting deeper in games, and with that I think he’s going to win a lot of games.”

Harvey just wants the ball.

“It was a long spring training and a long wait until I got back up here,” he said. “So [tonight] is going to be a lot of fun for me and I’m real excited about it, and after watching Niese out there I’m looking forward to my time.”